My second ds 4 is very much like this about Everything! It's on his terms, that's it! Until about 1 year ago, we thought maybe he was what a "normal" kid looked. He did meet many milestones before his brother, except lagged in speech.
I have seen bits of what he knows, but that's all. Ex. During a game when he was 3, he could show me that he could add and subtract. I found out he could count in Spanish to 20, when I overheard him counting... On the toilet. He is spelling, but not really reading. He led a pretty good discussion with his brother about what cosmos was about.
However, if I ask him anything that would demonstrate knowledge "I don't know" and "I can't" are the only responses I get. It is very frustrating to me.
All this leads me to worry about testing. I'm afraid he won't show his true ability. And he will need to be tested to be considered for the school his brother attends.
Also, from reading through the thread, I'm wondering if this is somewhat normal for the second child?
